1. Field of the Invention
This invention relates to an alloy target which is suitable for use in the manufacture of a magneto-optical recording medium by sputtering.
2. Description of the Prior Art
A magneto-optical memory has been drawing attention in recent years as it can facilitate the erasure and recording of information single-crystal materials such as garnets, polycrystalline materials such as MnBi and PtCo, and amorphous materials such as alloys of rare earth elements and transition metals are known as useful materials in making magneto-optical memories.
Of these materials, an amorphous alloy comprising a rare earth element and transition metal, for example, Tb-Fe-Co or Gd-Tb-Fe, provides a variety of advantages, for example, requiring only a small amount of energy for recording, being free from any grain-boundary noise, and providing the capability of producing large-sized material relatively easily.
As a method of manufacturing a thin film of such amorphous alloy, a sputtering method wherein ions collide against a target to form a thin film on a substrate positioned near the target is often used.
Target materials used in the sputtering technique should exhibit limited cracking, and a satisfactory uniform composition. One known material has a mixed structure comprising a phase of intermetallic compound of rare earth element and transition metal and a phase of transition metal alone (Japanese Laid-Open patent application No. Sho 62-70550).
However, the target material involves such drawbacks such that (1) the composition of the film obtained is greatly different from that of the target, (2) the permeability is so high that only a small magnetic flux leaks from the surface of the target, resulting in a low sputtering efficiency and thereby a reduced efficiency in using the target, especially when a magnetron sputtering device is employed; and (3) the surface of the target shows remarkable change in the shape regarding (2) above, which causes a change in the composition of the film with lapse of sputtering time.